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1、Optimization of a connecting rod by use of CATIA V5MF02-49 Mechanical definition of test case (connecting rod) CAD Parameterisation (CATIA V5) Structural analysis (CATIA V5) Optimisation workflow (modeFRONTIER) Analysis of resultsrlGEOMETRIC DATA:Crank r=50mmConnecting rod l=120mmPiston diameter D=5

2、4mmPOWER DATA:Engine power P=50KW2000rpmNumber of cylinders z=2Max combustion pressure Pc=21barPiston head mass m=0.30KgMmFcLOAD DATA:Combustion force Fc=Pc p D2 /4 = 4800N Inertial force(a =-p) Fin=mw2 r (cos a +r/lsin2 a )= mw2 r =600NMomentum force Fm=Mm/l=P/(w z)/l=1040NFcFmFinFillet radiusA tot

3、al of 9 geometric variables have been defined in biella2.CATPart CATIA fileSeveral geometric configurations can be obtained by the variation of these parametersRadial constraintsFmFc-FinStructural analysis is performed by CATIA in the linked file biella2.CATAnalysisInput variablesApplications chaino

4、utput variablesObjectives & constraintsCATIA node.CATPart file containing model.CATScript file for analysisparameters individuated by automatic introspectionouput variable (mass)Language=VBSCRIPTSub CATMain()Dim documents1 As DocumentsSet documents1 = CATIA.DocumentsDim analysisDocument1 As Document

5、Set analysisDocument1 = documents1.Open(D:usersalbertosimdesignbiella2.CATAnalysis)Dim analysisManager1 As AnalysisManagerSet analysisManager1 = analysisDocument1.AnalysisDim analysisModels1 As AnalysisModelsSet analysisModels1 = analysisManager1.AnalysisModelsDim analysisModel1 As AnalysisModelSet

6、analysisModel1 = analysisModels1.Item(1)Dim analysisCases1 As AnalysisCasesSet analysisCases1 = analysisModel1.AnalysisCasesDim analysisCase1 As AnalysisCaseSet analysisCase1 = analysisCases1.Item(1)analysisCase1.Compute Dim fileSystem1 As FileSystemSet fileSystem1 = CATIA.FileSystemDim folder1 As F

7、olderSet folder1 = fileSystem1.GetFolder(.)Dim analysisSets1 As AnalysisSetsSet analysisSets1 = analysisCase1.AnalysisSetsDim analysisSet1 As AnalysisSetSet analysisSet1 = analysisSets1.ItemByType(StaticSet)Dim analysisImages1 As AnalysisImagesSet analysisImages1 = analysisSet1.AnalysisImagesDim ana

8、lysisImage1 As AnalysisImageSet analysisImage1 = analysisImages1.Item(Sforzi alla Von Mises (valori nodali).1)analysisImage1.ExportData folder1, stress, txtEnd SubMacro3.CATScript open .CATAnalysis file run analysis read static set results write vonMises stresses in stress.txt fileCalc_maxstress_pyt

9、honm = -1.0e10infile = open(CWD + stress.txt,r)line = infile.readline()line = infile.readline()while infile: line = infile.readline() s = line.split() n = len(s) if n = 0: break a = float(s3) m = max(m,a)infile.close()max=mObjectives:- minimise mass of the connecting rod- minimise mean value of stre

10、ssConstraints:- max stress 70 N/mm2 (original geometry max stress)- conrod volume 0.034Kg (original geometry mass)ALGORITHMS:- MOGT (multi-objective game theory)A total of abot 280 designs have been performed with MOGTOriginal config.Mass 0.34 kgMax stress 70.1 N/mm2Best config.(MOGT)Mass 0.312 kgMax stress 56.4 N/mm2Original config.Mass 0.34 kgMax stress 70.1 N/mm2Best config.(MOGT)Volume 0.312mm3 Max stress 56.4 N/mm2The most important parameters seem to be the external side shape and the external fillet radius The optimisation of a connecting rod (minimise mass-minimis